The present invention relates to a rear projection television set in which a reflector mirror is provided behind a screen so that light from a projection source is projected through the reflector mirror to the rear side of the screen. Also, the present invention relates to a projection system which may be applied to a front projection television set as well as a rear projection television set in which performances such as overall brightness balance and color balance are well improved.
In general, in rear projection television sets, a projection source is provided in a lower portion of a casing, and light from the projection source is reflected by a reflector mirror so as to project the rear side of the screen. As shown in FIGS. 1 and 2, the rear projection television set has a casing 50. In a lower portion of the casing, there is provided a projection source 51 which is composed of a CRT unit 54 and a lens assembly 55. The light emitted from the projection source 51 is reflected by the reflector mirror 52 and is caused to pass through the screen 53 provided on a front face of the casing 50.
In such a rear projection television set, a ray of light 60 emitted from the projection source 51 along an optical axis will advance in a normal direction of the screen 53 or otherwise as shown in FIG. 2, will advance toward the screen 53 at an incident angle .theta..sub.0 relative to the normal line l.sub.0 of the screen from the lower side to the upper side. The incident angle .theta..sub.0 is usually set at about 5.degree., for example. The reason why the ray of light 60 is caused to advance along the normal line of the screen 53 or at a slight incident angle from the lower side to the upper side is that the observer may feel the pictorial image bright.
The projection source 51 is provided to be slanted from the screen side of the depth of the casing 50 to the central portion so that a ray of light 61 directed to a lower edge of the screen 53 is prevented from being blocked or interrupted by the projection source 51. However, in order to receive the projection source 51 below the screen 53, a so-called skirted portion (i.e., a lower space) is provided in the casing 50.
In general, a center height To of the screen 53 depends upon a height of the eyes of the observer and an optical path within the casing 50. For instance, the center height To is in the range of about 850-1,000 mm. For this reason, if a rack is provided in the lower space of the casing 50 for connection with a VTR, a laser disc player and the like, the center height To is unduly increased which is not practical. As a result, additional equipment such as VTRs and laser disc players have to be installed in another place.